This invention relates to a system and method for automatically steering or controlling a boat to direct the boat along a course so that the depth of water adjacent to the boat remains essentially constant at a pre-set selected depth. The invention has many potential uses, but has particular use with fishing boats where it is desired to fish at a selected depth while the boat is moving. A particularly preferred application of the invention is with recreational fishing boats where the user of the boat fishes while trolling. Such trolling is typically accomplished with electric trolling motors so that the present invention may be used in conjunction with a trolling motor for propelling and steering the boat along a course to automatically maintain a selected depth so that the user of the boat is free to fish without diverting his attention to driving the boat.
The desirability of fishing at a selected depth has long been known. Trolling motors have been used to move the boat slowly, and electronic depth finders have been used so that the operator of the boat could monitor the depth and manually steer the boat along a course in an effort to maintain a reasonably constant depth so that appropriate lures or bait could be presented to fish suspected to be present in the water at the selected depth. The problem with this technique is that it requires considerable attention by the operator such that the operator is diverted from the important task at hand, namely, fishing.
The present invention solves this problem, allowing the operator of the boat to devote attention to fishing while the boat is automatically steered along a course to maintain a selected depth.
Generally, in accordance with the invention the steering of the boat along the course to maintain the selected depth is accomplished by sensing the depth of the water adjacent the boat, such as by an ultrasonic or other type of ranging device. The information gathered by the ranging device is then transformed by suitable electronic circuitry to signals which automatically steer the boat, such as by turning a trolling motor, to move the boat along a course to maintain the selected depth. The invention automatically makes allowance for conditions where course changes are not desirable and provides course heading references from which course headings are changed and where limits are established restricting the degree of change to enhance the system's capability to maintain a course at the selected depth.
In accordance with the invention the operator of the boat directs the boat at an initial heading which is referred to herein as the initial baseline course heading which defines an initial course reference for the boat. Means are provided to the operator for inputting information into the system controller establishing a depth reference identifying shallower water as either on the left or right side of the boat. This information tells the controller whether shallower (or deeper) water is to the left or to the right of the initial baseline heading so that the controller can establish a new desired course heading in the proper direction as needed to maintain the selected depth. Means are also provided for the operator to input into the controller information representing a selected water depth to be maintained adjacent the boat as the boat moves along.
The system includes a ranging device, such as sonar or the like, for detecting the actual depth of the water adjacent the boat. Means are provided for comparing the actual depth with the selected depth and for detecting when the actual and selected depths are not equal. When the actual and selected depths remain unequal for a selected period of time, the system changes the course heading of the boat to a new desired course heading for the boat to follow. This new desired course heading is in a direction relative to the initial baseline heading so as to steer or move the boat in a direction toward equalizing the actual and selected depths based further on the input information as to whether shallower water is on the left or the right side of the boat. The new desired course heading is maintained for a selected time period while continuing to detect or measure the actual depth and comparing the actual depth with the selected depth. Preferably, the new desired course heading bears a pre-determined relationship to the initial baseline course heading and is selected to be within a pre-defined limit relative to the initial baseline heading. Further course changes to further new desired course headings are made, as needed, toward equalizing the actual and selected depths until the system detects that the actual and selected depths have become equal. When the actual and selected depths become equal resulting from a change to a new desired course heading, a new baseline course heading is established that bears a pre-determined relationship to the initial baseline course heading. The system establishes a new course heading for the boat, which may be the new baseline course heading, until a further change is needed to a new desired course heading in response to detecting that the actual and selected depths are no longer equal.
The system includes certain time delays to ensure that unnecessary course heading corrections are not made as might result, for example, where the bottom of the body of water is rough or uneven or where there is an abrupt but temporary change in depth due to a large rock, a hole, or the like.
Therefore, it is a primary object of this invention to provide a system and method which is accurate, reliable, and accommodates various conditions under which a boat is operated for automatically steering a boat along a course to maintain a selected depth.